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Studies on Downy Mildew of Gherkins Caused by Pseudoperonospora cubensis (Berk. And Curt.) Rostow.

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Title Studies on Downy Mildew of Gherkins Caused by Pseudoperonospora cubensis (Berk. And Curt.) Rostow.
 
Creator Santoshreddy Machenahalli
 
Contributor M.S.L. Rao
 
Subject Plant pathology
 
Description Gherkin or pickling cucumber (Cucumis sativus L.) is an exotic vegetable
being grown in several parts of Karnataka for export. This vegetable is suffering from
several economically important foliar diseases like downy mildew, which is posing a
serious threat to the successful large scale cultivation of this vegetable in Karnataka.
Survey results indicated that severity of gherkin downy mildew was more in Koppal
followed by Gadag, Haveri, Dharwad, Bellary, Bagalkot districts and the per cent
disease index varied from 63.21 to 70.58.
The disease starts from 20 days after sowing, almost all stages of the crop
were found to be susceptible. Among the fourteen genotypes evaluated against P.
cubensis, genotype ‘Sparta’ was found moderately resistant. Three genotypes viz.,
Vertina, Nun-5508 and Shakthi–RZ were found to be moderately susceptible. The
size of sporangia of P. cubensis from different hosts varied between 45-56 × 26-
37μm. The maximum sporangial germination observed at 20°C with 100 per cent
relative humidity.
Among the different fungicides, botanicals and bioagents tested against
P. cubensis, Fenamidon + Mancozeb, Metalaxyl + Mancozeb, garlic bulb extract and
Pseudomonas fluorescens were found superior, in inhibiting the sporangial
germination under in vitro condition. Integrated disease management study under
field conditions revealed that, the treatments with foliar sprays of Metalaxyl-
MZ®Fenamidon + mancozeb ® Dimethomorph at 0.2 per cent recorded least per
cent disease index which was found on par with Metalaxyl-MZ and Fenamidon +
Mancozeb spray alone. As the rotation of different molecules of fungicides avoids the
resistance development by the pathogen against fungicides, rotation of fungicides is
beneficial rather than the single molecule usage.
 
Date 2016-11-10T15:57:03Z
2016-11-10T15:57:03Z
2011
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/84939
 
Format application/pdf
 
Publisher UAS, Dharwad